The women said that Schwahn talked to them in traumatizing ways, and some of them are still in therapy for post-traumatic stress because of it.

The women were inspired to make a statement after a writer on the show tweeted about an unnamed showrunner who harassed female writers.

Stars of the teen soap "One Tree Hill," which ran from 2003 to 2012 on The WB and The CW, have united against its showrunner Mark Schwahn, accusing him of sexual harassment.

On Monday, Actresses Sophia Bush, Hilarie Burton, and Bethany Joy Lenz signed their names on a statement acknowledging Schwahn's alleged sexual harassment during the run of "One Tree Hill."

Over the weekend, "One Tree Hill" writer (and current "Crazy Ex-Girlfriend" writer) Audrey Wauchope tweeted that she and her writing partner Rachel Specter were regularly sexually harassed while working on the show, but she didn't name Schwahn in any of the tweets.

"He pet hair. He massaged shoulders," Wauchope wrote. "I know he did more but not to me so they're not my stories to share."

Bush, Burton, Joy Lenz, and Wauchope are just four of the 18 of the women who signed the statement. The statement says that Schwahn's behavior was an open secret on the show, and some of the women are still in treatment for post-traumatic stress.

"Many of us were put in uncomfortable positions and had to swiftly learn to fight back, sometimes physically, because it was made clear to us that the supervisors in the room were not the protectors they were supposed to be," the statement says. "Many of us were spoken to in ways that ran the spectrum from deeply upsetting, to traumatizing, to downright illegal. And a few of us were put in positions where we felt physically unsafe. More than one woman on our show had her career trajectory threatened."

"Believe women," the statement says. "We are all in this together." (Read the full statement at The Hollywood Reporter.)

Schwahn is currently the showrunner for "The Royals" on E!

In a statement, E! said, "We are monitoring the information carefully. E!, Universal Cable Productions and Lionsgate Television are committed to providing a safe working environment in which everyone is treated respectfully and professionally."